The invention relates generally to four stroke internal combustion engines which include, in the cylinder head, exhaust ports located in a surface which is inclined to the cylinder axis. In the past, machining of the inlet exhaust valve seats (in the inclined surface) surrounding the intake and outlet exhaust ports did not present a serious problem because the cylinders were fabricated separately from the cylinder block.
However, employment of inlet and exhaust valve seats in an inclined surface at the head end of a one-piece engine block presents serious problems.
Attention is directed to the following United States Patent list:
______________________________________ U.S. Pat. No. Inventor(s) Issue Date ______________________________________ 2,401,211 A. V. D. Willgoos May 28, 1946 2,456,272 A. T. Gregory December 14, 1948 3,691,914 Josef Reisacher September 19, 1972 3,674,000 Josef Reisacher July 4, 1972 3,897,770 Hermann Mettig August 5, 1975 4,092,956 Hans List June 6, 1978 4,230,087 Fumiyuki Abe October 28, 1980 4,294,203 Philip E. Jones October 13, 1981 4,365,594 Bertram Obermayer December 28, 1982 4,606,304 Hermann Kruger August 19, 1986 ______________________________________
Attention is also directed to Japanese Application No. 3-206473 filed Jul. 23, 1991.